1. Field of the Invention
The present invention is related to the field of the parts made of composite materials, and more particularly of the parts aimed at being assembled with other ones and likely to be subjected to tensile and/or compression forces.
Thus, the object of the present invention is such a part made of composite material aimed at being subjected, through at least one point of attachment, to tensile and/or compression forces, as well as the method for obtaining this part.
The present invention finds a particular application in the field of the manufacture of connecting rods, and thus another object is also a connecting rod made according to the inventive method.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
It is known that the weak point of the composite materials is the thermoplastic or thermosetting matrix in which reinforcing fibers are embedded, and which is generally made of a resin, because it has a specific strength that is much lower than that of the fibers. The way of ruining of a part made of a composite material is generally a fracture of the resin binding the fibers.
A good design of a composite part takes this phenomenon into consideration and favors a transmission of the forces by putting the fibers under pure tension or compression, which results into not stressing the resin. Thus, the composite material is formed of layers of fibers oriented in the direction of said forces or in directions close to the latter.
Though this can easily be done at the level of the essential portion of the part when the shapes are simple and the direction of the forces is controlled, it is difficult at the level of the areas of joining with one or several other parts, namely the areas in which the tensile or compression force is exerted.
In general, such a joining area includes an insert provided with a connecting means permitting to make the connection and the transmission of the forces into the part, but the putting in place of such inserts is particularly difficult, namely when the forces are aimed at changing in direction during the use of said composite part.
The main drawback is thus localized at the level of the joining of the body of the composite part with the insert, and is related to the transmission of the force from the one to the other.
Thus, from WO 2008/066606 is known a connecting rod comprising a tubular body made of composite material, each end of which a metallic insert is made integral with through mutually connected dual-shearing joints.
From U.S. Pat. No. 4,992,313 is also known a connecting rod formed of the winding of fibers about a mandrel comprising the inserts aimed at forming the eyes.
From FR 2 152 289 is also known a force-transmitting organ, such as a connecting rod, made of a fiber-reinforced synthetic material. This organ comprises a tubular central body containing fibers oriented according to the direction in which the forces are exerted, and the ends of which are narrowed in the form of a truncated cone in order to permit to make integral with each of them a connecting means, which is formed of two portions, an internal one and an external one, so as to be capable of enclosing the narrowed portion of the end of the tubular central body.
However, this force-transmitting organ only partially copes with the problems of joining the body of the composite part with the insert, and problems of long-term resistance and strength remain.
Also known are composite parts, in which the insert including the connecting means is embedded in the composite material the body is made of. Such composite parts only partially permit to cope with the problems of joining, because problems of discontinuity of the tensile and/or compression strength remain.
From US2005/056503 is also known a connecting rod formed of oriented reinforcing fibers embedded in a matrix, wound onto a mandrel, as well as an insert made by winding fibers, and aimed at forming an eye of said connecting rod, by being embedded in a hole provided for in the end of the latter. Such a connecting rod can in no way be subjected to tensile and/or compression forces, the more when the direction of the forces is intended to vary.